1. Field of the Invention
The invention relates generally to circulation valves and sliding sleeve tools. In particular aspects, the invention relates to the design of ball seats used in actuation mechanisms for such tools.
2. Description of the Related Art
Wellbore tools have been designed which are operated by the use of a ball or plug that is landed on a seat within the flowbore of the tool string. The ball or plug serves to increase pressure and/or redirect fluid flow through the tool in order to operate the tool. Tools of this type include circulation valves which are used to selectively open and close lateral fluid flow ports in a tool sub to permit fluid flowing axially through the tool to be diverted into the surrounding flowbore. Circulation valves of this type are described in U.S. Pat. No. 4,889,199 issued to Lee, U.S. Pat. No. 5,499,687 issued to Lee, U.S. Pat. No. 7,281,584 issued to McGarian et al. and U.S. Pat. No. 7,416,029 issued to Telfer et al.
The parent application to this one describes tools which operate by using balls or plugs of different sizes. The parent application to this one is U.S. patent application Ser. No. 12/826,020 filed Jun. 29, 2010, which is incorporated by reference in its entirety.